An integrated circuit comprises a switching transistor having an emitter connected to a grounding terminal, a first resistor connected between a first gate of a first field-effect transistor and the grounding terminal, a second resistor connected between the first gate of the field-effect transistor and a collector of the switching transistor, and a third resistor connected between the collector of the switching transistor and a drain of the field-effect transistor. The integrated circuit further comprises a bias voltage terminal connected to the collector of the switching transistor to apply a voltage to the bias voltage terminal from the outside of the integrated circuit via a sixth resistor.